Surface treatment for welding

ABSTRACT

This disclosure relates to electrical resistance welding and more particularly to the surface treatment of metal members along the faying and electrode engageable surfaces thereof. The faying surfaces are embossed or formed by a high energy rate method so as to be of a uniform finish whereby there will be a predetermined resistance between engaged faying surfaces thereby providing for a better control on the power required for forming a weld and the resultant metal weld.

United States Patent Paul M. Erlandson Palos Park, 111.

Feb. 5, 1969 Aug. 3, 1971 Continental Can Company, Inc New York, N.Y.

Inventor Appl. No. Filed Patented Assignee SURFACE TREATMENT FOR WELDING7 Claims, 4 Drawing Figs.

US. Cl 219/105, 219/482, 219/67, 219/93, 219/117 1nt.Cl 823k 11/02 FieldolSearch 219/105, 67, 78, 81-83, 91, 93, 1 17; 228/24; 29/482, 483, 488

References Cited UNITED STATES PATENTS 2,287,540 6/1942 Vang 219/105 X2,096,623 10/1937 Almdale 219/93x 2,897,340 7/1959 Krieger 219/93x2,999,146 9/1961 Kaplan etal 219/93 3,228,103 1/1966 Shewmon 29/488X3,400,449 9/1968 Maquire etal 29/488X Primary Examiner-R. F. StaublyAssistant ExaminerL. A. Schutzman Attorney-Diller, Brown, Ramik & HoltABSTRACT: This disclosure relates to electrical resistance welding andmore particularly to the surface treatment of metal members along thefaying and electrode engageable surfaces thereof. The faying surfacesare embossed or formed by a high energy rate method so as to be of auniform finish whereby there will be a predetermined resistance betweenengaged faying surfaces thereby providing for a better control on thepower required for forming a weld and the resultant metal weld.

HIGH ENERGY RnT FIG 1 MECHRNISM n B We ZFIGZ IHIIH H l 51'! 3 I L J @n m8/ mi HHIMI F INVENTOR 23 PAUL M. ERLHNDSON ATTORNEYS SURFACE TREATMENTFGR WELDING This invention particularly relates to the treatment ofsurfaces of metal members which are to be electrically resistance weldedtogether. The invention particularly relates to the welding together ofedge portions of relatively thin sheet metal to form a continuous seamutilizing roller electrodes.

In addition to the problem of assuring a good continuous weld, there isalso the problem of power loss and electrode life which must beconsidered from an economical standpoint. It will be readily apparentthat the pressures over the area contact between electrode andworkpieces must be limited in order to prevent undue electrodedeterioration. On the other hand, if a proper resistance weld is to beformed wherein melting is held to a minimum or is avoided, it isnecessary that the faying surfaces of the sheet metal being weldedtogether must have good contact resistance so as to obtain the desiredcombination of pressure and heat to perform the intended weld which ispreferably of the solid-state type or a close proximation thereof.

In the past, the surfaces have been prepared by grinding or by rotarymachine tool application. Such procedures have not provided either thedesired uniformity of finish or the smoothness of finish desired.Furthermore, such procedures have also left the minute depressions inthe metal filled with the dust resulting from the grinding or machiningoperation with the result that the desired contact between fayingsurfaces has not been obtained.

In accordance with this invention, it is proposed to emboss at least thefaying surfaces of. the sheet metal to be welded together so as to breakup any surface oxides, etc., and at the same time to increase thesmoothness of the surface which is being treated while showing theuniformity of the finish thereof. It is preferred that the embossing beaccomplished by high energy rate metal-forming process both for thepurpose of providing best control for the embossed finish, but also inorder to assure the rapid embossing of the metal sheet.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claimed subjectmatter, and the several views illustrated in the accompanying drawing.

IN THE DRAWING:

FIG. I is an elevational view of an apparatus for embossing edgeportions ofa metal can by the blank utilizing a high energy rate metalforming process.

FIG. 2 is a plan view of the can body blank showing generally the extentof the treated edge portions, the edge portions being widened forpurposes ofclarity.

FIG. 3 is an enlarged fragmentary vertical sectional view taken alongthe line 3-3 of FIG. 2 and schematically shows the finish of theembossed edge portions of the body blank.

FIG. 4 is a schematic sectional view showing the manner in which thetreated edge portions of the body blank are continuously welded togetherby means ofa pair of roller electrodes.

Referring now to FIG. 2 in particular, it will be seen that there isillustrated a can body blank 5 which is adapted to he rolled into agenerally cylindrical form and then have the edges thereof continuouslywelded together in overlapped relation. This is accomplished by firsttacking together the overlapped edges of the body blank 5 and thenpassing the overlapped edges between a pair of roller electrodes 6 and 7in the manner best shown in FIG. 4.

It will be readily apparent from FIG. 4 that the can body blank 5 hasfour critical edge surfaces. These include an inner electrode engageablesurface 8, an inner faying surface 9, an outer faying surface It) and anouter electrode engageable surface II. It will be readily apparent thatin the connections between the electrodes 6 and 7 and the body blank 5,three electrical joints are formed. These include the joint between theelectrode 7 and the inner electrode engageable surface 8, the jointbetween the faying surfaces 9 and It), and the joint between the outerelectrode engageable surface II and the electrode 6. It will also beapparent that in a given electrical welding system, these joints are theonly variables and in order to obtain better controlled weldingoperations, control of the resistances of these joints is not onlyhighly desirable, but also necessary.

In accordance with this invention, it is proposed to control theelectrical resistances of the three above-mentioned joints, particularlythat between the faying surfaces 9 and 10, by maintaining a fine controlon the surface roughness of the edge surface portions of the body blank.It has been found that this can be best accomplished by embossing thesurfaces. While any suitable embossing operation which is of a controluniformity may be utilized, it is preferred that the embossing beperformed by means of a high energy rate metal forming process.

Referring now to FIG. ll, it will be seen that there is schematicallyillustrated a high energy rate metal-forming apparatus which willperform the desired embossing operations. The apparatus is generallyreferred to by the numeral 12 and includes a base 18 having upstandingedge guide portions M for controlling the position of a. body blank 5 orlike sheet metal member which is to have the edges thereof treated. Thebase 13 is provided with a pair of hardened inserts 15 and 16 which havethe upper surfaces thereof configurated so as to emboss the edge portionsurfaces 9 and 11, respectively, of the body blank 5.

The body blank 5 may be conveyed to, positioned on and removed from abase 113 by means of a suitable feed mechanism 17 which may be of anyconventional type including the type presently being utilized in canbody-forming mechanisms.

The apparatus 12 also includes a hammer member 18 which carries alongthe oppositesides thereof hardened removable die members 20 and 21 whichare vertically aligned with the inserts of die members 15 and 16,respectively. The hammer 18 is vertically reciprocated in any suitablemanner, but preferably by means of a high energy rate actuatingmechanism, such as an electrohydraulic actuator.

It will be readily apparent from FIG. 1 that when the body blank 5 ispositioned within the apparatus 12, the hammer 18 will beinstantaneously moved downwardly and all four edge surface portions ofthe body blank 5 treated at the same time. The operation of theapparatus 12 may by synchronized with the feeding of the-body blanks 5to the body forming and welding machine. Embossing may be done on thefly" if a very high speed electrohydraulic system is employed.

At thistime it is pointed out that while it is the purpose of thisinvention to obtain uniformity of surface finish of the edge portions ofthe body blank 5, it is not absolutely necessary that the surfaces 8 andIll thereof be treated in the manner described herein. However, undernormal conditions, the four surfaces would all be treated inasmuch asthis may be readily accomplished in a single operation.

With particular reference to FIG. 3 and general reference to FIG. 4, itis to be understood that in addition to design uniformity of finish ofthesurfaces of the edge portions of the body blank 5, it is preferredthat the faying surfaces 9 and 10 have an extremely fine finish ascompared to that which is normally permissible. It has been found that afinish on the order of 1.0 micron or less provides for a bestcombination of pressure and heat required to form a weld or at the sametime provides for a maximum powerefficiency. When available, a finish onthe order of 0.2 micron would be desired for the faying surfaces 9 and10.

When it is found desirable to emboss the surfaces 8 and 11, theembossment should be of a rougher pattern to lower the contactresistance of the surfaces 8 and l I with the roller electrodes 7 and 6,respectively.

It is also pointed out at this time that no specific pattern ofembossment has been illustrated and no specific pattern is required. Itis merely necessary that the pattern be determined and thereafter thesame pattern to be utilized so that uniformity of resistance will beobtained.

Referring once again to FIG. 3 in particular, it will be seen that theopposite surfaces of the body blank 5 are provided with suitablecoatings 22 and 23. These coatings are protective coatings and need notextend into the embossed areas, If they do, they must be removed priorto the embossment.

it is further pointed out here that in certain instances it may bedesirable to provide other treatment for the embossed surfaces,including chemical treatment. It will be readily apparent that all looseor thick, or gross surface deposits, whether oxides, oil, scale, etc.,must be removed. in addition, it may be desirable to provide chemicaltreatment which will create conditions to insure further uniformity ofresistance to contact areas of the body blank.

Although the invention has only been schematically illustrated anddescribed, it is readily apparent that the degree and design ofembossment will be varied to meet ones own particular requirements andtherefore no further description hereof is necessary. Further, althoughonly one preferred embodiment of the invention has been specificallyillustrated and between metal members which includes the steps ofpreparing faying surfaces of the members, bringing the faying surfacestogether under a controlled pressure loading, and coupling the membersto a source of electrical energy to resistance heat and weld togetherthe members along the faying surfaces; the improvement residing inembossing the faying surface to an overall uniform roughness.

2. The process of claim 1 wherein the faying surfaces are prepared byhigh energy rate metal forming.

3. The process of claim 1 wherein the faying surfaces have a finish onthe order of 1 micron and less centerline average.

4. The process of claim 1 wherein the faying surfaces have a finish onthe order of 0.2 micron centerline average.

5. The process of claim 1 wherein electrode engageable surfaces of themembers remote from the faying surfaces are also prepared to a uniformroughness of a greater roughness than the roughness of the fayingsurfaces.

6. The method of claim 5 wherein each faying surface and the associatedelectrode engageable surface are simultaneously formed in a singleoperation.

7. The process ofclaim 1 wherein any protective coating existing on themetal members is removed prior to the preparing of the faying surfacesto a uniform roughness.

1. In a process of providing uniform resistance welds between metalmembers which includes the steps of preparing faying surfaces of themembers, bringing the faying surfaces together under a controlledpressure loading, and coupling the members to a source of electricalenergy to resistance heat and weld together the members along the fayingsurfaces; the improvement residing in embossing the faying surface to anoverall uniform roughness.
 2. The process of claim 1 wherein the fayingsurfaces are prepared by high energy rate metal forming.
 3. The processof claim 1 wherein the faying surfaces have a finish on the order of 1micron and less centerline average.
 4. The process of claim 1 whereinthe faying surfaces have a finish on the order of 0.2 micron centerlineaverage.
 5. The process of claim 1 wherein electrode engageable surfacesof the members remote from the faying surfaces are also prepared to auniform roughness of a greater roughness than the roughness of thefaying surfaces.
 6. The method of claim 5 wherein each faying surfaceand the associated electrode engageable surface are simultaneouslyformed in a single operation.
 7. The proceSs of claim 1 wherein anyprotective coating existing on the metal members is removed prior to thepreparing of the faying surfaces to a uniform roughness.